Control of air quantities supplied by ventilating installations



April 27, 1965 J. KNARBAKK CONTROL OF AIR QUANTITIES SUPPLIED BY VENTILATING INSTALLATIONS 2 Sheets-Sheet 1 Filed N0v. 1, 1961 FIG. 7

April 27, 1965 J. KNARBAKK 3,180,363

CONTROL OF AIR QUANTITIES sUPPLIED BY VENTILATING INSTALLATIONS Filed Nov. 1. 1961 2 Sheets-Sheet 2 ATTORNEYS United States Patent 3 Claims. (Cl. 138-46) The present invention concerns improvements relating to the control of air quantities supplied by ventilating installations, especially installations of the type which supply several separate rooms with ventilating air from a common source of compressed air and where the flow of air must pass through a mat of porous material, which has one or more penetrable faces.

In installations of the above mentioned type unbalance will occur if the pressure prevailing in any one of the rooms suddenly drops, e.g. owing to doors or windows thereof being opened. If this happens a disproportionally great part "of the air will be supplied to the room in which low pressure occurs, and the other rooms will be supplied with less than the calculated amount of air. An inversed effect occurs if windows are opened in a wall front against which wind pressure is acting, since the pressure in the room is then increased and the room receives less air, whereas the other rooms receive increased supply of ventilating air.

Moreover an installation of the above mentioned type will have a higher pressure in the first part of the air distributing not than in the last part thereof, especially in installations operating with high air speed, so that rooms connected to the first part of the air distributing net receives a greater quantity of ventilating air per valve than rooms connected to the last part of the air distributing net.

Air valves are lmown, which are provided with means for controllingthe quantity of air passing therethrough by automatic control of the free area of the valve as a function of the pressure in the supply channel and/or at the place where the air is blown into the room. In these known arrangements the pressure acts upon membranes or other pressure responsive organs which in turn, through pneumatic or electric amplification, control a flap valve, which varies the flow area. Further the British patent specification No. 863,937 discloses an arrangement for control of air quantities supplied by a ventilating installation where automatic control is obtained thereby that the air supply path is obstructed by a porous material which at increasing pressure ratio is compressed against a perforated support, so that the pore openings of said material are constricted and the resistance to the penetration of the air is increased.

The object of the present invention is to provide, in a manner similar to that of said British Patent No. 863,937, a simple and cheap form of control for installations of the above defined type, which needs no more or less complicated control organs.

According to the invention this is achieved thereby that the porous mat is freely spanned in such manner that upon increasing differential air pressure parts of the exterior surfaces thereof are pressed against each other, or against purposely provided surfaces not penetrable to air.

By suitable choice of the properties of the porous material, e.g. its thickness, shape and penetrability, it is possible to secure an approximately constant supply of air to the several rooms connected to an installation of the above mentioned type, independent of pressure variations which might occur in each room or supply channel.

Using the above described principle it is also possible to slacken or tighten, by means of a controllable spanning device, the penetrable mat surfaces, whereby the valve may be adjusted for a greater or smaller quantity of air flowing therethrough. As a result of the slackening or tightening of the mat of porous material, a lower or higher pressure difierential through the valve, respectively, is necessary in order to press faces of the mat against each other or against surfaces impenetrable to air.

In addition to the above mentioned advantages there is obtained dampening of sounds which might occur due to the shape of the air path or channel, since such sounds will be absorbed by the porous material. Moreover a certain filtering action is obtained.

The invention is explained below in connection with certain embodiments thereof shown in the drawings, in which:

FIG. 1 is a broken sectional view through an arrangement constructed in accordance with the invention;

FIG. 2 is a broken sectional view taken on the line lIII of FIG. 1;

FIG. 3 is a broken sectional view of another embodiment of a valve arrangement according to the invention;

FIG. 4 is a broken sectional view similar to that of FIG. 1 showing an embodiment constituting a modification of that shown in FIGS. 1 and 2; and

FIG. 5 is a broken sectional view of a further embodi ment showing a modified form of valve construction according to the invention.

The drawing as shown in FIGS. 1 and 2 illustrates a a usual air inlet valve 1, provided with guiding ribs 2, 3 for the air current and inserted in a wall of one of the rooms connected to the ventilating arrangement. The valves are supplied with pressured air through the channel 4. At the pressure side, in front of the guiding ribs, the pressure reducing and flow controlling arrangement is provided. Said arrangement consists of a spanning arrangement or device which may comprise a rigid frame 5 rigidly connected to a spanning rib or list 6 by a support 9 carried on a cross bar 10, the ends of which are attached to the frame 5. The marginal edge portion of the porous mat 7 is tightly secured to the frame 5 and is by means of the list 6 so extended towards the air current that opposite faces of said mat include an acute angle therebetween. Thus said faces may be pressed towards each other, beginning at the apex of the top angle, by increasing air pressure, as indicated by dotted lines in FIG. 1, whereby the eifective flow-through area of the porous mat is reduced. The'porous mat 7 may consist of foam plastic, foam rubber, a porous mass of felt or the like, eventually arranged in several layers. Between the spanning list 6 and the frame 5 the support 9 is provided with an adjustable screw connection 8, by means of which the air-penetrable portions of porous mat may be straightened, tightened or slackened, to adjust the valve for a desired greater or smaller constant throughfiow quantity of air.

The principle of the invention is not bound to the construction described above, which may be modified in various ways. While the preferred form of the invention is illustrated in FIGS. 1 and 2, the principle of the invention may be carried out in modified forms of construction. For example, FIG. 3 illustrates a form of construction in which the edges of a mat 12 are attached to the sides of a channel 4, the mat comprising an accordion-like structure extending across the channel and presenting several air-penetrable faces which may be pressed more or less against each other as the pressure of the air flowing through the channel increases, as indicated by the dot and dash lines on the downstream side of the mat.

In the embodiment illustrated in FIG. 4, the margin of a mat of porous material 13 is secured to a channel '4, While the mat proper extends in the channel in the shape of a cone, in the direction opposite to the direction of air flow." The .tip of the cone-shaped mat 13 is sup ported on a supporting member 14, corresponding to the support 9 in FIGS. 1 and 2. Upon increase in air flow through the channel 4', portions of the conical-shaped mat are pressed in so they engage in the manner illuss trated by the dot and dash lines.

In the embodiment illustrated in FIG. 5 the air channel 4 is provided with an enlargement 15, the lower rim of which carries inwardly-extending air-impenetrable plates or members 16 leaving 'an outlet directly below the end of the channel 4. In this construction the margin of a mat 17 of porous material is attached to the lower end of the channel 4, as shown, and normally'has the shape shown in full lines. The members 1-6 have surfaces facing the lower portion of the mat 17 and upon increase in air pressure flowing against the mat, its shape is distorted so that it engages the members 16,- for example in the position shown in dot and dash lines, so

that the effective flow area through the mat 17 is reduced.v

in response to an increase in the air pressure on the pressure side of the mat to a position in which its downstream surface is in engagement with the down-stream surface of a separate portion of the area of the mat, thereby preventing the fiow of air through said firstmentioned portion of the mat and reducing the area of the mat through which air may flow.

2. In an air ventilating installation including an airflow channel through which air flows under pressure, a self-adjusting "means for controlling the air flow through the channel comprising an air penetrable mat of porous material mounted in the channel with its margin fixed with respect to the inner periphery of the channel so that the air flowing through the channel must flow through the mat, said mat of porous material extending in the channel from the position of it's margin in a direction opposite to the direction of air flow in the channel, means 1 for supporting the extendedportion of the mat in a manner' to present down-stream surfaces of portions thereof facing each other, said portions being movable to engage.

portions of ,their said surfaces with each other in re 7 spouse to an increase in the airpressure on the pressure In all embodiments, upon increased pressure drop through the mat, portions of the penetrable faces are pressed against each other or'against said inserted impenetrable' faces, whereby the effective flow-through area means for controlling the air fiow-through the channel comprising an air penetrable mat of porous material mounted in the channel and through which the air flowing in the channel must flow, said mat of porous material being extended in said channel, a portion of the area of the mat through which air normally flows being movable side of the mat, whereby the portions of the mat With engaging surfaces become impenetrable to the flow of air and the total flow-'through'area of the mat is reduced.

3. An installation as claimed in claim 2, characterized in that said supporting means includes an adjusting means for changing the tension on the mat to in turn change the normal air flow through the mat.

References Cited by the Examiner V UNITED STATES PATENTS EDWARD v. BENHAM, Primary Examiner. 

1. IN AN AIR VENTILATING INSTALLATION INCLUDING AN AIR FLOW CHANNEL THROUGH WHICH AIR FLOWS UNDER PRESSURE, MEANS FOR CONTROLLING THE AIR FLOW THROUGH THE CHANNEL COMPRISING AN AIR PENETRABLE MAT OF POROUS MATERIAL MOUNTED IN THE CHANNEL AND THROUGH WHICH THE AIR FLOWING IN THE CHANNEL MUST FLOW, SAID MAT OF POROUS MATERIAL BEING EXTENDED IN SAID CHANNEL, A PORTION OF THE AREA OF THE MAT THROUGH WHICH AIR NORMALLY FLOWS BEING MOVABLE IN RESPONSE TO AN INCREASE IN THE AIR PRESSURE ON THE PRESSURE SIDE OF THE MAT TO A POSITION IN WHICH IT DOWNSTREAM SURFACE IS IN ENGAGEMENT WITH THE DOWN-STREAM SURFACE OF A SEPARATE PORTION OF THE AREA OF THE MAT, THEREBY PREVENTING THE FLOW OF AIR THROUGH SAID FIRSTMENTIONED PORTION OF THE MAT AND REDUCING THE AREA OF THE MAT THROUGH WHICH AIR MAY FLOW. 